1/*
  2 * Random Number Generator driver for the Keystone SOC
  3 *
  4 * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com
  5 *
  6 * Authors:	Sandeep Nair
  7 *		Vitaly Andrianov
  8 *
  9 * This program is free software; you can redistribute it and/or
 10 * modify it under the terms of the GNU General Public License
 11 * version 2 as published by the Free Software Foundation.
 12 *
 13 * This program is distributed in the hope that it will be useful, but
 14 * WITHOUT ANY WARRANTY; without even the implied warranty of
 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 16 * General Public License for more details.
 17 */
 18
 19#include <linux/hw_random.h>
 20#include <linux/kernel.h>
 21#include <linux/module.h>
 22#include <linux/io.h>
 23#include <linux/platform_device.h>
 24#include <linux/clk.h>
 25#include <linux/pm_runtime.h>
 26#include <linux/err.h>
 27#include <linux/regmap.h>
 28#include <linux/mfd/syscon.h>
 29#include <linux/of.h>
 30#include <linux/of_address.h>
 31#include <linux/delay.h>
 32
 33#define SA_CMD_STATUS_OFS			0x8
 34
 35/* TRNG enable control in SA System module*/
 36#define SA_CMD_STATUS_REG_TRNG_ENABLE		BIT(3)
 37
 38/* TRNG start control in TRNG module */
 39#define TRNG_CNTL_REG_TRNG_ENABLE		BIT(10)
 40
 41/* Data ready indicator in STATUS register */
 42#define TRNG_STATUS_REG_READY			BIT(0)
 43
 44/* Data ready clear control in INTACK register */
 45#define TRNG_INTACK_REG_READY			BIT(0)
 46
 47/*
 48 * Number of samples taken to gather entropy during startup.
 49 * If value is 0, the number of samples is 2^24 else
 50 * equals value times 2^8.
 51 */
 52#define TRNG_DEF_STARTUP_CYCLES			0
 53#define TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT	16
 54
 55/*
 56 * Minimum number of samples taken to regenerate entropy
 57 * If value is 0, the number of samples is 2^24 else
 58 * equals value times 2^6.
 59 */
 60#define TRNG_DEF_MIN_REFILL_CYCLES		1
 61#define TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT	0
 62
 63/*
 64 * Maximum number of samples taken to regenerate entropy
 65 * If value is 0, the number of samples is 2^24 else
 66 * equals value times 2^8.
 67 */
 68#define TRNG_DEF_MAX_REFILL_CYCLES		0
 69#define TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT	16
 70
 71/* Number of CLK input cycles between samples */
 72#define TRNG_DEF_CLK_DIV_CYCLES			0
 73#define TRNG_CFG_REG_SAMPLE_DIV_SHIFT		8
 74
 75/* Maximum retries to get rng data */
 76#define SA_MAX_RNG_DATA_RETRIES			5
 77/* Delay between retries (in usecs) */
 78#define SA_RNG_DATA_RETRY_DELAY			5
 79
 80struct trng_regs {
 81	u32	output_l;
 82	u32	output_h;
 83	u32	status;
 84	u32	intmask;
 85	u32	intack;
 86	u32	control;
 87	u32	config;
 88};
 89
 90struct ks_sa_rng {
 91	struct device	*dev;
 92	struct hwrng	rng;
 93	struct clk	*clk;
 94	struct regmap	*regmap_cfg;
 95	struct trng_regs *reg_rng;
 96};
 97
 98static int ks_sa_rng_init(struct hwrng *rng)
 99{
100	u32 value;
101	struct device *dev = (struct device *)rng->priv;
102	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
103
104	/* Enable RNG module */
105	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
106			  SA_CMD_STATUS_REG_TRNG_ENABLE,
107			  SA_CMD_STATUS_REG_TRNG_ENABLE);
108
109	/* Configure RNG module */
110	writel(0, &ks_sa_rng->reg_rng->control);
111	value = TRNG_DEF_STARTUP_CYCLES << TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT;
112	writel(value, &ks_sa_rng->reg_rng->control);
113
114	value =	(TRNG_DEF_MIN_REFILL_CYCLES <<
115		 TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT) |
116		(TRNG_DEF_MAX_REFILL_CYCLES <<
117		 TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT) |
118		(TRNG_DEF_CLK_DIV_CYCLES <<
119		 TRNG_CFG_REG_SAMPLE_DIV_SHIFT);
120
121	writel(value, &ks_sa_rng->reg_rng->config);
122
123	/* Disable all interrupts from TRNG */
124	writel(0, &ks_sa_rng->reg_rng->intmask);
125
126	/* Enable RNG */
127	value = readl(&ks_sa_rng->reg_rng->control);
128	value |= TRNG_CNTL_REG_TRNG_ENABLE;
129	writel(value, &ks_sa_rng->reg_rng->control);
130
131	return 0;
132}
133
134static void ks_sa_rng_cleanup(struct hwrng *rng)
135{
136	struct device *dev = (struct device *)rng->priv;
137	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
138
139	/* Disable RNG */
140	writel(0, &ks_sa_rng->reg_rng->control);
141	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
142			  SA_CMD_STATUS_REG_TRNG_ENABLE, 0);
143}
144
145static int ks_sa_rng_data_read(struct hwrng *rng, u32 *data)
146{
147	struct device *dev = (struct device *)rng->priv;
148	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
149
150	/* Read random data */
151	data[0] = readl(&ks_sa_rng->reg_rng->output_l);
152	data[1] = readl(&ks_sa_rng->reg_rng->output_h);
153
154	writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);
155
156	return sizeof(u32) * 2;
157}
158
159static int ks_sa_rng_data_present(struct hwrng *rng, int wait)
160{
161	struct device *dev = (struct device *)rng->priv;
162	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
163
164	u32	ready;
165	int	j;
166
167	for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {
168		ready = readl(&ks_sa_rng->reg_rng->status);
169		ready &= TRNG_STATUS_REG_READY;
170
171		if (ready || !wait)
172			break;
173
174		udelay(SA_RNG_DATA_RETRY_DELAY);
175	}
176
177	return ready;
178}
179
180static int ks_sa_rng_probe(struct platform_device *pdev)
181{
182	struct ks_sa_rng	*ks_sa_rng;
183	struct device		*dev = &pdev->dev;
184	int			ret;
185	struct resource		*mem;
186
187	ks_sa_rng = devm_kzalloc(dev, sizeof(*ks_sa_rng), GFP_KERNEL);
188	if (!ks_sa_rng)
189		return -ENOMEM;
190
191	ks_sa_rng->dev = dev;
192	ks_sa_rng->rng = (struct hwrng) {
193		.name = "ks_sa_hwrng",
194		.init = ks_sa_rng_init,
195		.data_read = ks_sa_rng_data_read,
196		.data_present = ks_sa_rng_data_present,
197		.cleanup = ks_sa_rng_cleanup,
198	};
199	ks_sa_rng->rng.priv = (unsigned long)dev;
200
201	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
202	ks_sa_rng->reg_rng = devm_ioremap_resource(dev, mem);
203	if (IS_ERR(ks_sa_rng->reg_rng))
204		return PTR_ERR(ks_sa_rng->reg_rng);
205
206	ks_sa_rng->regmap_cfg =
207		syscon_regmap_lookup_by_phandle(dev->of_node,
208						"ti,syscon-sa-cfg");
209
210	if (IS_ERR(ks_sa_rng->regmap_cfg)) {
211		dev_err(dev, "syscon_node_to_regmap failed\n");
212		return -EINVAL;
213	}
214
215	pm_runtime_enable(dev);
216	ret = pm_runtime_get_sync(dev);
217	if (ret < 0) {
218		dev_err(dev, "Failed to enable SA power-domain\n");
219		pm_runtime_disable(dev);
220		return ret;
221	}
222
223	platform_set_drvdata(pdev, ks_sa_rng);
224
225	return devm_hwrng_register(&pdev->dev, &ks_sa_rng->rng);
226}
227
228static int ks_sa_rng_remove(struct platform_device *pdev)
229{
230	pm_runtime_put_sync(&pdev->dev);
231	pm_runtime_disable(&pdev->dev);
232
233	return 0;
234}
235
236static const struct of_device_id ks_sa_rng_dt_match[] = {
237	{
238		.compatible = "ti,keystone-rng",
239	},
240	{ },
241};
242MODULE_DEVICE_TABLE(of, ks_sa_rng_dt_match);
243
244static struct platform_driver ks_sa_rng_driver = {
245	.driver		= {
246		.name	= "ks-sa-rng",
247		.of_match_table = ks_sa_rng_dt_match,
248	},
249	.probe		= ks_sa_rng_probe,
250	.remove		= ks_sa_rng_remove,
251};
252
253module_platform_driver(ks_sa_rng_driver);
254
255MODULE_DESCRIPTION("Keystone NETCP SA H/W Random Number Generator driver");
256MODULE_AUTHOR("Vitaly Andrianov <vitalya@ti.com>");
257MODULE_LICENSE("GPL");